Date Published: March 27, 2017
Publisher: Public Library of Science
Author(s): María Teresa Ramírez-López, Mariam Vázquez, Ermelinda Lomazzo, Clementine Hofmann, Rosario Noemi Blanco, Francisco Alén, María Antón, Juan Decara, Rocío Arco, Laura Orio, Juan Suárez, Beat Lutz, Raquel Gómez de Heras, Laura Bindila, Fernando Rodríguez de Fonseca, Cristina Óvilo.
Undernutrition during pregnancy has been associated to increased vulnerability to develop metabolic and behavior alterations later in life. The endocannabinoid system might play an important role in these processes. Therefore, we investigated the effects of a moderate maternal calorie-restricted diet on the levels of the endocannabinoid 2-arachidonoyl glycerol (2-AG), arachidonic acid (AA) and the N-acylethanolamines (NAEs) anandamide (AEA), oleoylethanolamide (OEA) and palmitoylethanolamide (PEA) in the brain of newborn rat offspring. We focused on brain structures involved in metabolism, feeding behavior, as well as emotional and cognitive responses. Female Wistar rats were assigned during the entire pregnancy to either control diet (C) or restriction diet (R), consisting of a 20% calorie-restricted diet. Weight gain and caloric intake of rat dams were monitored and birth outcomes were assessed. 2-AG, AA and NAE levels were measured in hypothalamus, hippocampus and olfactory bulb of the offspring. R dams displayed lower gain weight from the middle pregnancy and consumed less calories during the entire pregnancy. Offspring from R dams were underweight at birth, but litter size was unaffected. In hypothalamus, R male offspring displayed decreased levels of AA and OEA, with no change in the levels of the endocannabinoids 2-AG and AEA. R female exhibited decreased 2-AG and PEA levels. The opposite was found in the hippocampus, where R male displayed increased 2-AG and AA levels, and R female exhibited elevated levels of AEA, AA and PEA. In the olfactory bulb, only R female presented decreased levels of AEA, AA and PEA. Therefore, a moderate diet restriction during the entire pregnancy alters differentially the endocannabinoids and/or endocannabinoid-related lipids in hypothalamus and hippocampus of the underweight offspring, similarly in both sexes, whereas sex-specific alterations occur in the olfactory bulb. Consequently, endocannabinoid and endocannabinoid-related lipid signaling alterations might be involved in the long-term and sexual dimorphism effects commonly observed after undernutrition and low birth weight.
Decades ago, Barker and colleagues demonstrated a strong and paradoxical correlation between low birth weight and the development of metabolic syndrome in adulthood . Simultaneously, Dutch Famine cohort studies showed the long-lasting and deleterious effects of undernutrition during early development . These investigations led to propose the DOHaD (Developmental origin of Health and Disease) hypothesis, stating that early life insults could lead to increased vulnerability to develop diseases later in life  through a process known as programming . Extensive investigations in this area have focused on the effects of undernutrition in the fetal period. Particularly, it has been shown that poor nutritional environment in pregnancy is commonly associated to low birth weight, and to the development of metabolic diseases, such as obesity and metabolic syndrome , whose prevalence is reaching epidemic proportions worldwide .
This study was approved by the Animal Ethics Committee of the Complutense University of Madrid and was conducted in compliance with the European Directive 2010/63/EU on the protection of animals used for scientific purposes and according to the Spanish regulations (RD 53/2013 and 178/2004).
The main finding of the present study is that newborn rats exposed to a moderate caloric restriction during the entire pregnancy displayed alterations in endocannabinoids and/or endocannabinoid-related lipids, in brain structures involved in the regulation of metabolism and emotional and cognitive responses. Specifically, male and female offspring from diet-restricted dams exhibited decreased levels of the main endocannabinoids, their precursor and/or NAEs in the hypothalamus and, conversely, they showed enhanced content of these lipids in the hippocampus. This similar profile between males and females from calorie-restricted dams was not evident in the olfactory bulb, where the calorie-restricted female offspring presented decreased levels of AEA, their precursor (AA) and PEA. Moreover, these modifications were accompanied of underweight at birth, a common result when diet restriction is applied for the entire pregnancy or in the last phases of pregnancy [12, 13]. Interestingly, this finding has been widely associated to metabolic and behavioral abnormalities later in life [12–14].
In summary, we have demonstrated that a moderate caloric restriction during the entire pregnancy results in underweight offspring with altered endocannabinoid, AA and/or NAE levels in the hypothalamus, hippocampus and/or olfactory bulb of male and female offspring at birth in a sex-specific manner. These data represent a first step towards understanding the possible contribution of the ECS in the nutritional programming, considering the available data on the long-lasting effects of undernutrition and underweight at birth. Understanding why dietary manipulations modify hypothalamic, hippocampal and olfactory bulb endocannabinoid and endocannabinoid-related lipid levels, and whether these changes lead to permanent dysfunctions in the ECS and/or impairment in circuitries involved in the regulation of metabolism and emotional behaviors in a sex-specific manner need to be elucidated. Therefore, further investigations are required to clarify the role of the ECS in nutritional programming.